Foundry sand, additive, and method of treating foundry sand



United States Patent FOUNDRY SAND, ADDITIVE, AND' METHOD 7 OF TREATING FOUNDRY SAND Harry H. Johnson, Milwaukee, Wis., assignor to Walter Gerlinger, Inc., Milwaukee, Wis., a corporation of Wisconsin v No Drawing. Application April 30, 1952, Serial No. 285,327

7 Claims. 01. 106-385) This invention relates to a composition of foundry sand, to a foundry sand additive, and to a method of treating or conditioning foundry sand with an additive. This application is a continuation in part of my co-pending application Serial Number 225,455, filed May 9, 1951, now abandoned, and entitled Foundry Sand, Additive and Method of Treating Foundry Sand.

The invention consists in the mixture with foundry mold and core sand of an additive which includes a combustible non-adhesive and non-coking flour, desirably soft wood flour, impregnated and desirably saturated with petroleum derivative having a paraffin or asphaltic base.

The object of the invention is to produce better castings more reliably and at lower expense than has been possible in the past. Soft wood flour has not heretofore been regarded as suitable for the purpose because of its tendency to coke, to exude pitch, and to absorb costly oils from the core, thereby weakening the core, and consuming expensive oil. The petroleum derivatives used in the present invention for impregnation are also known to the art but, when used as herein disclosed, the resulting foundry sand additive secures better results than any heretofore used and costs about half as much as the best previously known. The improved results include a better distribution of the additive throughout the sand, the chemical elimination of oxygen from air trapped in the mold, the increased flowability of the sand in the making of the mold, with reduced requirements for added water, unimpaired bond strength of the sand, unimpaired reuse of the sand (coking renders it unusable), and the production of uniformly smooth surfaced castings free of wrinkles or blemishes and adhering sand.

In the preferred practice of the present invention, combustible lightweight non-adhesive flour, desirably of 80-100 mesh; soft wood flour or flour made from ground corn cobs being examples, is mixed in a muller with an impregnating petroleum derivative until all of the petroleum is absorbed. By non-adhesive I mean a flour that contains no starches or other material that mixed with water or oil will become adhesive. The foundry sand, of course, contains moisture and any adhesive mixed therein would impair flowability. Soft wood flour is preferred because of its low density and large number of cells. The

from the core. All previous attempts to use soft wood flour as an additive have failed because of such absorption or because of coking.

Any petroleum product havinga parafiin or asphaltic base may be used but liquid petroleum derivatives of relatively heavy viscosity are preferred. A desirable material is the hydrocarbon liquid solution of plasticizable resin disclosed in Weston Patent 2,444,413, granted July 6, 1948, and which has been uesd separately, and in relatively much higher proportions, as a foundry sand additive. Other examples are fuel oils such as are known to include types which have paraflin base and types which have an asphaltic base. The viscosity should desirably be about S. A. E. or heavier. If unduly viscous at the prevailing temperature the oil may be thinned with any mineral spirits or other solvents. My preferred practice is to admix the liquid solution of the Weston patent with a heavy fuel oil to comprise a solution consisting of 60% by weight of the liquid solution of the Weston patent and by weight of a heavy fuel such as No. 6 or Bunker C fuel oil. No. 6 fuel oil, as tested according to ASTM D 396-48T has a flash point of 150 F., a percentage by volume of water and sediment of 2%, a viscosity measured at 122 F. by a Furol viscosity instrument of 30, a specific group rated at a minimum by the XPT of 92, and a residual ash of .10 by weight. Of course, either the liquid solution of the Weston patent or the fuel oil could be used alone but I have found that the physical mixture above identified is satisfactory and produces optimum results at minimum cost.

Thus, the preferred composition of the additive comprises by weight:

70-84% soft wood flour, 80-100 mesh 16-30% of a mixture of 60% of the liquid solutionof U. S. Pat. 2,444,413, and 40% fuel oil A small percent of the additive as thus made, comprising the flour, impregnated with the petroleum derivative, is then mechanically dispersed throughout the sand from which the mold is to be made. In order not to interfere with the bond strength of the sand, I do not recommend the use of the additive in a greater amount than 3% by fiour is desirably saturated with the petroleum as hereinafter explained. The desirable range of proportions is 16% to 30% petroleum to 70% to 84% by weight of the soft wood flour. Because such flour is so light, its mass is great and this facilitates distribution throughout the sand. The lower limit of 16% represents about the minimum amount of petroleum derivative which will satisfactorily be usable, even without full accomplishment of the objectives of the invention. The 30% figure is about the upper limit needed to saturate the softest of wood flours, but the invention contemplates enough petroleum to produce flour saturation, whatever proportion might be necessary for a particular flour. Saturation of the flour with the petroleum is important as saturated flour will not absorb any of the water from the mold or costly core oils weight of the sand. To assure the presence of a suificient quantity of additive, I do not use less than 1% by weight ordinarily, or less than /2 of 1% in special cases, such as core blowing. The preferred proportion is 2% of the additive. Within these ranges, the additive will be present in sufficient volume and distribution to insure flash and the production of voids in the mold as needed to accommodate thermal expansion of the sand, and additionally, the reduction of the oxygen present, thereby precluding adhesion of the sand to the casting made in the mold. As a result, the casting will have an exceptionally clean, smooth surface which will not ordinarily require excessive grinding or sand blasting.

The soft wood or equivalent flour is so much lighter than the facings heretofore used that a given weight of my improved additive is much more widely and uniformly distributed throughout the sand. In addition, it flashes virtually instantly to accommodate sand expansion from the moment such expansion commences.

The impregnation of the soft light flour with petroleum derivative not only expedites the flash and oxygen reduction but prevents coking and pitching heretofore experienced in attempts to use soft wood flour facing. Also, as aforestated, saturation of the flour with the petroleum prevents absorption by the flour of costly core oils. In addition, the impregnation makes the flour water-repellent and gives it antifriction qualities which materially increase flowability of the mixture of sand and additive in the making of the mold. This, in turn, minimizes the moisture requirements and eliminates the problems heretofore experienced because of the need for substantial quantities of water in the sand. This sand treated by my additive is moldable at low water content levels. Moreover, the presence: of the additive helps .prevent water evaporation from .the .sand. Hence, desired water levels may 'be maintained in sand treated with my additive for longer periods than heretofore.

Inasmuch as the mixture is more easily effected, and .is lightened by the additive used, the total work required to mull the mixture uniformly is far less than has heretofore beenneeded with sea-coal facings and is even easier than the mulling of sand and a resin coating such as that disclosed in the Weston patent. Assuming that the same resin solution .be used as the hydrocarbon derivative with which my flour is impregnated, the cost is obviously very much reduced by the use of the present invention, since i merely treat 2 of the total, more or less, with the Weston resinous solution, instead of treating the entire mass of sand. Better dispersion and oxygen absorption and at least equally good flash are achieved.

In both cores and molds the presence .of my petroleum impregnated flour has no eflfect on clay, bentonite, or cereal and oil binders normally present therein. This is important because in all attempts heretofore to use the liquid solution of the Weston patent or fuel oil alone (without impregnating non-adhesive flours as herein disclosed) the presence of these petroleum products detracts from binding strength and weakens the mold and core. Neither does the presence of my additive increase mold strength whereby to increase labor and cleaning costs, or result in scrap castings due to failure of the mold to collapse. The absence of ash and coking structures after flash eliminates rough castings and ultimate discard of sand. In addition use of my additive increases the ram density of the cores and molds, thus preventing metal penetration.

I claim:

1. The'method-of preparing foundry sand which comprises impregnating the discrete particles of a combustible non-adhesive flour to substantial saturation with a liquid petroleum derivative, and then thoroughly dispersing the discrete particles of impregnated flour into the sand.

2. The preparation of a foundry sand composition which comprises the step of rendering Water resistant a fine fiour of vegetable origin by impregnating discrete flour particles to substantial saturation by agitation of such particles with a liquid petroleum derivative in the proportionsby weight of 16 to 30% of the petroleum deriva tive and 70 tov 84% of the flour, said impregnated flour being subject to flash on exposure to heat, and the subsequent addition of the impregnated flour to molding sand in the proportions by weight of A of 1% to 3% of the flour to 97 to 99% of the sand, and the thorough admixture of the impregnated flour and sand to uniformly disperse the discrete particles of impregnated flour in the sand.

3. The method of-claim 2 wherein the petroleum derivative comprises a physical mixture of hydrocarbon liquid solution of plasticizable :resin and :-fuel oil.

4. A foundry sand additive comprising :an absorptive combustible non-adhesive and substantially non-absorbent flour of vegetable origin impregnated with a liquid petroleum derivativeaand substantially saturated therewith, said additive constituting non-adhesive discrete particles of impregnated flour suitable for dispersion as discrete particles in the foundry sand.

5. The product defined in claim 4 in which the petroleum derivative is selected from a group consisting of derivatives having a paratfin base and derivatives having an asphaltic base.

6. The product of claim 4 in which the petroleum derivative comprises a hydrocarbon liquid solution of plasticizable resin in the proportion by weight of 16 to 30% of the total weight of the product.

7. Amolding sand comprising a combustible substantially non-absorbent and non-adhesive flour, the discrete particles of which are impregnated to substantial saturation with a liquid petroleum derivative, in combination with foundry sand in a mixture wherein the discrete particles of impregnated flour are uniformly dispersed in the sand and constitute approximately /2 of 1% to 3% of the total by weight and is subject to flash on exposure to molten metal pouredinto the mold.

References Cited in the file of this patent UNITED STATES PATENTS 1,401,791 Kirschbraun Dec. 27, 1921 2,033,870 Smith Mar. 10, 1936 2,087,088 Greider et al July 13, 1937 2,422,118 Meyer June 10, 1947 2,444,413 Weston July 6, 1948 2,465,094 Hartwig Mar. 22, 1949 2,510,220 'Grube June 6, 1950 2,622,963 Wallace Dec. 23, 1952 FOREIGN PATENTS 41,680 Germany Nov. 23, 1887 

1. THE METHOD OF PREPARING FOUNDRY SAND WHICH COMPRISES IMPREGNATING THE DISCRETE PARTICLES OF A COMBUSTIBLE NON-ADHESIVE FLOUR TO SUBSTANTIAL SATURATION WITH A LIQUID PETROLEUM DERIVATIVE, AND THEN THOROUGHLY DISPERSING THE DISCRETE PARTICLES OF IMPREGNATED FLOUR INTO THE SAND. 